Machines for compression molding sealing liners within closure shells typically include a turret or carousel that rotates around a vertical axis. A plurality of molds are provided around the periphery of the carousel in the form of male and female mold sections that are aligned along vertical axes parallel to the axis of rotation. Cams drive one or both of the mold sections of each pair between an open position, in which a molded part is removed from the mold and a premade shell and a charge of plastic liner material are placed in the female mold section, and a closed position in which the male and female mold sections are brought together to compression mold the liner within the shell. A machine of this type is illustrated, for example, in U.S. Pat. No. 5,451,360.
Although vertical axis carousel-type machines of the noted type have enjoyed substantial commercial acceptance and success, innovation remains desirable. In particular, in vertical axis carousel-type machines, the weight of the rotating equipment is parallel to the vertical axis of rotation, creating a bending moment with respect to the axis of rotation and the bearings and shaft that support the carousel. Carousel-type machines also require a substantial amount of valuable floor space in a manufacturing facility. It is a general object of the present invention to provide an apparatus and method for compression molding sealing liners within premade closure shells that reduce the forces applied to the support frame and bearings, and/or reduce maintenance requirements and the amount of energy needed to operate the machine, and/or reduce the amount of floor space required per machine.
The present invention involves a number of aspects that can be implemented separately from or in combination with each other.
An apparatus for compression molding sealing liners in premade closure shells, in accordance with a first aspect of presently preferred embodiments of the invention, includes a shell loader for presenting premade closure shells in sequence, a mold charge placement device for placing charges of liner material into the premade shells, and a vertical wheel molding machine for receiving the closure shells in sequence from the loader and compression molding the mold charges to form sealing liners within the closure shells. The vertical wheel molding machine preferably includes a wheel mounted for rotation around a horizontal axis and a plurality of angularly spaced molds disposed around the wheel. Each of the molds preferably includes a first mold segment and a second mold segment disposed radially outwardly of the first mold segment. One of the first and second mold segments, preferably the second mold segment, is a female mold segment that includes a nest for receiving a premade closure shell. The other of the first and second mold segments, preferably the first mold segment, is a male mold segment that includes a core for engaging and compression molding the mold charge of liner material within the shell. In two disclosed embodiments of the invention, the mold charge of liner material either is placed within the premade closure shell prior to placement of the shell within the nest, or is placed within the shell after placement of the shell in the nest, preferably by placing the mold charge in a pocket on the mold core. The second mold segments preferably are moved radially inwardly and outwardly by at least one cam disposed adjacent to the wheel for engaging the second mold segments as the wheel rotates around its axis.
A method of compression molding sealing liners within premade closure shells, in accordance with another aspect of the invention, includes providing a wheel mounted for rotation around a horizontal axis and a plurality of angularly spaced molds disposed around the wheel. Each of the molds includes a first mold segment and a second mold segment disposed radially outwardly of the first mold segment. As the wheel is rotated around its horizontal axis, the second mold segments are moved in sequence radially with respect to the associated first mold segments between a radially inner closed position and a radially outer open position spaced from the associated first mold segment. With the mold segments in the open position, closure shells with compression molded sealing liners are removed from the mold, and a premade closure shell and mold charge of liner material are placed in the mold. The mold segments are then closed as the wheel rotates to compression mold the mold charge of liner material between the mold segments. In the disclosed embodiments of the invention, the mold charge of liner material is placed into the premade shells either before or after placing the shells into the molds.